The electronic circuit apparatus comprises a printed-circuit board in most cases, which comprises an electronic circuit mounted on its top surface and a ground-pattern stuck to its bottom surface, serving as a common return path of a signal current caused by the electronic circuit. The printed-circuit board is contained in a shield-case, which protects the electronic circuit from external noise and prevents electromagnetic radiation from the printed-circuit board. The printed-circuit board is communicated with an external electronic circuit by a cable, which is fixed to the printed-circuit board via a connector mounted thereon. The dominant component of the impedance of the ground-pattern is an inductive reactance and directly proportional to frequency. On account of recent tendency that the bit-rate of digital signal is remarkably increasing, electromagnetic radiation from the electronic circuit apparatus via the cable connected thereto, which is caused by a voltage between both the ends of the ground-pattern, becomes an important problem. Although considerable numbers of efforts have been made in order to bring this problem to a settlement, further improvement is extremely desirable.